Method and apparatus for measuring and controlling the volume of a liquid segment in a tube

Abstract

A method for measuring or controlling the volume of a liquid segment confined within a tube and having a leading edge and a trailing edge. The tube is exposed to radiation at an angle and radiation refracted from the inner surface of the tube is measured at the leading and trailing edges of the segment while the liquid segment is moving through the tube.

What is claimed is: 
     
       1. A method for determining the volume of a liquid segment traversing at a constant velocity through a transparent tube having an inner wall using a radiation detector, the segment having a leading edge and a trailing edge, comprising the steps of: exposing the tube to an incident wave from a source of radiation;   locating the source of radiation at an azimuthal angle .O slashed. that maximizes the amount of radiation reaching the detector, the angle .O slashed. being the angle formed between the incident wave from the source of radiation and the refracted wave from the inner wall of the tube;   detecting refracted waves from the source that are refracted at the inner wall of the tube; and,   comparing the amount of radiation refracted from the tube at the leading and trailing edges of the segment with the amount of radiation refracted from the tube when there is no liquid segment within the tube,   so that the volume of the segment may be determined from the time interval between passage of the leading and trailing edges of the segment past a position along the tube, in combination with the internal diameter of the tube and the constant velocity of the segment.   
     
     
       2. The method of claim 1 further comprising the step of magnifying the beam refracted radiation from the tube by a factor ranging between 1 and 100 times before the step of detecting measuring the amount of radiation. 
     
     
       3. The method of claim 1 further comprising the step of collimating the beam refracted radiation from the tube by an amount ranging between 60 and 99 percent before the step of detecting the amount of radiation. 
     
     
       4. The method of claim 1 further comprising controlling the traversing of the liquid so that the volumes of a plurality of consecutive liquid segments are a constant volume. 
     
     
       5. The method of claim 1 wherein the volume of the liquid segment is in the range of 100 nanoliter to 1 microliter. 
     
     
       6. The method of claim 1 wherein the radiation has wavelengths between 0.4 and 1.2 microns. 
     
     
       7. The method of claim 1 wherein the liquid segment comprises liquids having a refractive index in the range 1 to 1.8. 
     
     
       8. The method of claim 1 wherein the liquid segment comprises whole blood, serum, urine, water, glycerol, or aqueous reagents. 
     
     
       9. An apparatus for determining the volume of a liquid segment traversing at a constant velocity through a transparent tube having an inner wall, the segment having a leading edge and a trailing edge, comprising: a single radiation detector for measuring an amount of radiation refracted from the inner wall of the tube;   a source of radiation located at an azimuthal angle .O slashed. that maximizes the amount of radiation reaching the detector, the angle .O slashed. being the angle formed between the source of radiation and the radiation refracted from the inner wall of the tube; and,   means for comparing the amount of radiation refracted from the inner wall of the tube at the leading and trailing edges of the segment with the amount of radiation refracted from the inner wall of the tube when there is no liquid segment within the tube, so that the distance between the leading and trailing edges of the segment traversing past a position along the tube may be determined from the constant velocity.   
     
     
       10. The apparatus of claim 9 further comprising means for controlling the traversing of the liquid so that the volume of the liquid segment is a predetermined volume. 
     
     
       11. The apparatus of claim 9, further comprising means for magnifying the radiation refracted from the tube by a factor ranging between 1 and 100 times. 
     
     
       12. The apparatus of claim 9, further comprising means for collimating the radiation refracted from the tube by an amount ranging between 60 and 99 percent. 
     
     
       13. The apparatus of claim 9 wherein the radiation has wavelengths between 0.4 and 1.2 microns.